Editor's Note: This post is the third in a series by Kim R. Holmes taking a "new look" at American foreign policy. It is based on ideas developed in his forthcoming book, Rebound: Getting America Back to Great, which will be published this fall. The author is a distinguished fellow at the Heritage Foundation and a former U.S. assistant secretary of state for international organization affairs.

In the first two installments of this series I described how existing ways of looking at and practicing American foreign policy are changing. The old liberal-conservative divide is blurring on such issues as military interventions, civil liberties, defense spending, and the purposes of American power in the world. In this post I would like to speculate on some implications for the future.

First a caveat: We are not about to witness a liberal-conservative convergence across the board in foreign policy. The two worldviews are still too far apart and anchored in very different ideological roots. Regardless of new developments, both sides will remain politically wary of each other. Moreover, as the old saying goes, "The enemy gets a vote." An attack out of the blue, as happened on 9/11, or an economic meltdown at home could upset existing trends, making all this speculation moot.

Nevertheless, provided things remain the same, new lines of communication may be possible on certain issues. At the top of the list is the big question: What is the purpose of American power? Typically liberals were distrustful of American power unless it was constrained in some way or redirected toward some humanitarian goal. Yet advocacy of humanitarian military operations is not as popular as it once was, particularly in Barack Obama's White House. On the other side of the spectrum, conservatives typically were big believers in the exercise of American power for spreading freedom and democracy. Yet here, too, with the rise of the libertarian right, there is less enthusiasm.

Is there any middle ground here?

I think possibly so. Common ground could be found by more narrowly defining the purposes of American power -- especially military power. Rather than arguing that American power exists to engineer the domestic arrangements of foreign countries or to fulfill largely stated humanitarian goals, we accept that it is mainly to maintain a global balance of power in America's favor. The goals would be to support the country's allies, keep the sea lanes open, and prevent hostile powers or terrorists from harming America or overturning the existing international order. With this more modest strategy the country could find itself with fewer military interventions of "choice," whether for humanitarian or other purposes, not because it doesn't want to pay for them or because it fears "quagmires," but because the country feels it doesn't need them.

At the same time we agree that the United States absolutely must maintain military strength second to none, not because we want to police the world, but because it is necessary in order to safeguard Americans' security and liberty. Dropped would be not only the more utopian expectations of American power, but also the tendency to treat it as a source of trouble in the world.

It is vital that we reach consensus on the purposes of American power. Without it, ideological and political divisions could lead to the worst of all possible worlds. For example, libertarian-minded conservatives could team up with liberals to gut the defense budget and unwittingly produce a slow drift toward strategic decline. Or interventionist-minded conservatives could team up with humanitarian liberals and involve ever-diminishing U.S. forces in unnecessary and fruitless wars. Neither extreme is in America's interest, yet because of existing divisions, they are likely to be the choices the country faces.

What would a new common ground look like? It would accept that indeed there are limits to the utility of American power, especially in terms of what military interventions can achieve, but there would be also recognition that a strong military is needed not only to defend the United States and its allies, but to maintain a global order in America's favor. It would concede that savings could be achieved by reforming the Pentagon, but the Defense Department would not be treated as a cash cow to fund more social programs. Put in check would be the "responsibility to protect" agenda of humanitarian liberals, but also the "freedom agenda" of some neoconservatives. Distinctions would have to be made. Using force in Syria would likely not make the common ground list, nor would interventions to stop a humanitarian crisis in Africa or elsewhere. But it could be a different story with respect to a hostile nuclear Iran.

Strategic modesty could produce a truce in another area of foreign policy. For decades American liberals have been firm believers in international governance and the United Nations. Yet as we have seen with the Obama administration, there is a lot more talk than action. In a new age of lower expectations, might there not be a willingness to admit that some of the old utopian goals of the U.N. are outdated? By the same token, might not conservatives learn to accept that the U.N. indeed has some legitimate activities, such as establishing technical standards, providing food aid after a massive natural disaster, helping with refugees, alleviating humanitarian disasters, and providing real peacekeeping that succeeds in finding a permanent end to hostilities?

Strategic modesty has implications for both left and right. But to realize those outcomes will require open minds. For the first time in a very long time, we may be able to have a real conversation about issues that were once taboo. It would be good for the country and the world if we did. We simply must find a way for liberals and conservatives to come together so that America continues as a great power and world leader far into the future.

-Kim R. Holmes is a former assistant secretary of state, is a distinguished fellow at the Heritage Foundation.